Would have been nice to have Mark Zuckerberg at Christchurch call - Robertson

It would have been nice to have Mark Zuckerberg at the Prime Minister's Christchurch call summit, but it's fine he's not there, Grant Robertson says.

It was announced on Sunday the Facebook founder and CEO won't be going and will instead be sending head of global affairs Nick Clegg.

Robertson, taking over the Prime Minister's regular Tuesday slot on The AM Show, said it's okay Zuckerberg won't make it.

"I know that Facebook will be represented at a pretty senior level and you'll be aware that the Prime Minister's also had direct conversations with Mark Zuckerberg.

"Of course it would have been good for him to be there, he'll have his reasons for not being able to."

Jacinda Ardern is leading the Christchurch Call summit as a response the March terror attack on two Christchurch mosques, which saw 51 people killed in a shooting spree livestreamed on Facebook.

Robertson said all the major tech companies would be represented at the summit - Facebook, Twitter, Google, Microsoft among others.

But Newshub Political Editor Tova O'Brien said the Zuckerberg no-show meant the summit got off to a rough start.

"I've got to say it's got off to a pretty bad start when we realised that Mark Zuckerberg isn't going to be here, he's sending his global affairs guy...

"He was in France last week as well, talking to Emmanuel Macron, the French president, he could have stayed on for a couple of days - it would have been a gesture of goodwill."

What will come out of the summit remains to be seen, although O'Brien said it will likely focus on livestreaming violent acts.

Robertson didn't rule out taking regulatory action in New Zealand if need be as well.

"I'd hope we don't get to that, the point being that this is a global thing. The whole thing about the internet is countries have to be able to act together to resolve this.

Major changes like blocking Facebook livestreaming services in New Zealand could be more difficult than the simple technical aspects though, O'Brien said.

"I think [blocking Facebook live] would be politically unpalatable and probably socially unpalatable, certainly one of the extreme actions that the United Kingdom is considering if something like this happened.

"The Prime Minister's saying that she's looking at all of the international examples, not really talking about the costs or benefits of any of them yet."